1. Field of the Invention
This invention relates to magnetic position sensing apparatus and in particular to such apparatus for producing and sensing a magnetic field which varies with position of a movable element.
2. Description of Related Art
It has become common practice to utilize magnetic field sensing devices, such as Hall cells, to detect the proximity of movable metallic members. Magnetic position sensing apparatus using such sensing devices are also known. However, such apparatus typically sense fringe magnetic fields and are adversely affected by stray magnetic fields. Thus they cannot make accurate position measurements in noisy environments, such as under the hoods of automobiles where extraneous magnetic fields of substantial magnitude emanate from the generator, the ignition system and various other components.
Such known magnetic position sensing apparatus are also functionally limited. Typically each known type of apparatus is capable of producing only one type of output signal, such as an output signal which varies linearly over a specific range of positions. It would be advantageous if a magnetic position sensing apparatus could be tailored to produce any one of a variety of output waveforms (e.g. linear, exponential, sinusoidal) over a selectable range of positions.